Volume 6, No. 1 (2005)

APPROCHES SYNTHETIQUES ALTERNATIVES ET COMPLEMENTAIRES VERS LES ARISTOLACTAMES

RYBALKO-ROSEN HÉLÉNE, COUTURE AXEL, GRANDCLAUDON PIERRE*

Two conceptually new synthetic approaches to alkaloids aristolactam has been developed. They differ from the synthetic tactics employed for the construction of common precursors i.e. haloarylmethylene isoindolinones. These highly conjugated systems have been obtained by Horner reaction or E1cb elimination involving phosphorylated or dephosphorylated isoindolinones respectively. Free radical cyclization completes the synthesis of the target fused aristolactams.

EXPLORATION CONFORMATIONNELLE DES HETEROCYLES MOYENS MIXTES (N, O et S) A 8 CHAINONS ACCOLE A UN MOTIF CYCLOHEXENIQUE PAR LA MODELISATION MOLECULAIRE

ABDELMALEK O.(1), DIBI A.(2), LABBASSI M.(2)

Conformational analysis of mixed medium heterocycles from 8 links joined to the cyclohexenic cycle was carried out using the mechanics calculations. The results show that those with trans jonction are the most stable and the less strained, whereas those with trans jonction in the cycle sulfur (X=S) have the higher conformational mobility. A diastereoselectivity has been observed in these heterocycles, where one observes an important predominance of the diastereoisomere trans in relation to the cis for the heterocycles nitrogen (X=N) and oxygen (X=O), whereas it is the diastereoisomere cis that is relatively predominant in the cycle sulfur (X=S).

RESISTANCE A LA CORROSION DES ALLIAGES UTILISES COMME IMPLANTS EN MILIEU BIOLOGIQUE

CHAOUKI HAKIMA, CHTAINI A., EL BOUADILI A.

The surface properties and the resistance to corrosion of a metal or alloy are primary determined by their biocompatibility and their behavior in a biological environment. In the organism electrochemical reactions may occur. The biological fluids are electrolytic environments, they assuring the ionic conductivity. Several physical chemical characteristics of these environments, such as the redox potential, the electric conductivity and the pH have a big influence upon the corrosion phenomenon. In this paper, we have studied the corrosion resistance of steel and copper in biological environments containing amino acids. The electrochemical methods used were the abandon potential, the polarization curves and the impedance measurements.

MODELING OF ACID GASES ABSORPTION COLUMN USING ALKANOLAMINE SOLUTIONS

VINEL D.J., BOUALLOU CHAKIB*

This work is devoted to the improvement of acid gases removal process by alkanolamine solutions, especially DiEthanolAmine (DEA) and MethylDiEthanolAmine (MDEA). A new rigorous model treating reactive absorption based on modified two-film theory is developed as a first step. This model uses Nernst-Planck equations for the liquid film and Stefan-Maxwell equations for the gas film. The program was developed to handle either kinetically controlled or instantaneous chemical reactions in the liquid film. In a second step, the model is introduced within a simulator of industrial column; the new numerical tool thus developed makes it possible to represent successfully the cases of industrial absorption columns in term of absorption rates and enhancement factors.

ARTIFICIAL NEURAL NETWORK MODELING FOR DENSITY OF SOME BINARY SYSTEMS

LISA GABRIELA(1), CURTEANU SILVIA(2)

This paper presents experimental results of density for three binary systems: toluene - n-propanol, toluene - iso-propanol and toluene - propanoic acid. In order to obtain density values at different temperature and concentrations, empirical models were developed using experimental data. Two types of models were built and compared: feedforward neural networks and empirical equations which give the dependence of density on temperature and concentration. Accurate results were obtained in training and validation phases, using neural networks with simple topologies and short training time. In addition, the trend of the predicted densities was qualitatively consistent. The empirical equations also provide good concordance between simulation results and experimental data.

INFLUENCE DE LA MATIERE SECHE DANS LE LAIT SUR LA CROISSANCE ET L’ACTIVITE FERMENTATIVE DES BIFIDOBACTERIES

BARASCU E.

In this study was monitored the growth and the activity of bifidobacteria in reconstituted milk, with different content of nonfat dry milk, in order to obtain optimal conditions of culture for this bacteria. In addition, the possibility to obtaining the useful date for the technology of probiotic milks, fermented with bifidobacteria in pure cultures, was evaluated. In the present, the most probiotic fermented milks available in the marketplace contain mixed cultures of bifidobacteria and other lactic acid bacteria. Milk with 12.4% nonfat dry milk provides the most numbering population of bifidobacteria. The utilization of nonfat dry milk in concentration more than 12.4% is not justified because the growth of bifidobacteria is not proportional with the addition of nonfat dry milk. The developed acidity during the incubation was greatest in the same sample (with 12% nonfat dry milk) and this was correlated with the best growth of bifidobacteria.

EFFET DU SUPPLEMENT DU MIEL SUR LA CROISSANCE ET L’ACTIVITE DES BIFIDOBACTERIES DANS LE LAIT

BARASCU E.

In this study the growth and metabolic activity of bifidobacteria were monitored in milk containing polyflower honey, with the intention to use results in technology of symbiotic fermented milks, because this natural syrup is a source of prebiotics. In addition, using the natural ingredients like honey to the manufacture of fermented milks seems to be an attractive solution to meet the consumers with a variety of healthy foods. The addition of honey improved the growth of bifidobacteria in milk and bacterial populations obtained in samples with 1% and 2% honey are higher than in milk without sweetness. In the case of metabolic activity of bifidobacteria, the stimulation effect of honey was more pronounced than the one of the growth of these bacteria, and the acidity developed during the incubation was the greatest in the sample with 1% honey.

ELECTROCHEMICAL REDUCTION OF CF2Br2 IN THE PRESENCE OF RICH OR DEFICIENT OLEFINS

MEDAGHRI-ALAOUI A.(1)AND(2), CALAS P.(1), CHOUKROUN H.(1), COMMEYRAS A.(1), VERPEAUX J. N.(3), AMATORE C.(3)

In the presence of an olefin, CF2Br. radicals add to the double bond with a constant rate that depends only modestly on the olefin nature (1-hexene, 2.3-dimethyl-2-butene and ethylacrylate). However, the fate of the radical adduct depends on the nature of the olefin and controls the nature of the main electrolysis product(s). For 1-hexene, the radical adduct abstract a Br-atom from the parent CF2Br2. This triggers a rapid radical chain reaction, which results overall in the addition of CF2Br2 across the double bond. For ethylacrylate, the radical adduct ads to the parent olefin, which initiate oligomerisation. For 2.3-dimethyl-2-butene, the radical adduct undergoes dismutation. Cyclopropanation is observed only with 2.3- dimethyl-2-butene and corresponds to a fast trapping of the carbene CF2 before it may react with DMF. For the two other olefins, reaction of CF2 with DMF is preferred.